JPWO2010098236A1 - Metal-coated polyimide resin substrate with excellent heat aging characteristics - Google Patents

Abstract

After surface modification by a dry method on one or both sides of a polyimide resin film, a barrier layer is formed by a dry method, and then a seed layer is formed by a wet method or a dry method, and the surface layer is conductive by a wet method. A metal-coated polyimide resin substrate having a film formed thereon, and a time-of-flight secondary ion mass spectrometer (TOF-SIMS) on a peeling surface on the conductive film layer side after the 90 ° peel test of the metal-coated polyimide resin substrate ), The mixed layer thickness of the polyimide residue and the barrier metal layer residue is 0.70 nm or less in terms of Si sputtering rate, and the peel strength retention rate after the aging test at 150 ° C. and 168 hours (150 A metal-coated polyimide resin substrate having a peel strength after initializing at 168 ° C / initial peel strength) of 50% or more is provided. To.

Description

  The present invention relates to a method for producing a non-adhesive flexible laminate material used as a mounting material for electronic components such as flexible printed circuit boards, TAB, and COF, particularly a metal-coated polyimide resin substrate having excellent heat aging characteristics.

  FCCL (Flexible Copper Clad Laminate) in which a metal conductor layer mainly made of copper is laminated on a polyimide film is widely used as a material for circuit boards in the electronics industry. Among these, non-adhesive flexible laminates (especially two-layer flexible laminates) that do not have an adhesive layer between a polyimide film and a metal layer have attracted attention as the circuit wiring width becomes finer.

As a method for producing an adhesive-free flexible laminate, particularly an adhesive-free flexible laminate corresponding to fine pitch, a barrier layer and a seed layer are previously formed on a polyimide resin film by a dry plating method such as sputtering, CVD, and vapor deposition. There is a so-called metalizing method in which a metal layer to be a conductor layer is formed by an electrolytic plating method.
In this metallizing method, in order to increase the adhesion between the metal layer and the polyimide film, the polyimide resin film surface is subjected to plasma treatment prior to the formation of the metal layer for the purpose of improving the adhesion with the barrier metal. Surface modification has been performed (see Patent Document 1 and Patent Document 2).

In addition, it has also been proposed that a barrier layer and a seed layer are previously formed on a polyimide resin film by electroless plating, and then a metal layer to be a conductor layer is formed by electrolytic plating.
In this method, prior to the formation of the metal layer, the polyimide resin film is immersed in a solution made of an alkali metal hydroxide to improve the adsorption of the catalyst, which becomes the driving force for the subsequent electroless plating, and the adhesion to the barrier metal. Surface modification for the purpose of improvement is performed (see Patent Document 3).

  The surface modification treatment of the polyimide resin film has a great influence on the adhesion between the polyimide resin film and the metal layer, and is a particularly important treatment step in production.

As the mechanical properties required for adhesive-free flexible laminates, the initial peel strength and the peel strength after a long period of time are important. In recent years, the peel strength after a long period of time has become particularly important as a requirement for high reliability. It is coming.
Moreover, as a method for evaluating peel strength after a long period of time, it is generally evaluated by peel measurement after heat aging (150 ° C., 168 hours), which is an accelerated deterioration test.

Recently, the modified polyimide resin film is dyed with an aqueous silver nitrate solution, the cross section is observed with a transmission electron microscope (TEM), and the peel strength after initial and after heat aging is determined by the thickness of the modified layer. A method has been proposed (see Patent Document 4).
However, in the actual surface modification of the polyimide resin film, those having various molecular structures including functional groups that contribute to adhesion are generated depending on the processing conditions. The layer was evaluated only with a specific substance, and there was a problem that even if the modified layer thickness in the above evaluation was the same, there was a difference between the actual peel strength test results.

Japanese Patent No. 3173511 Special table 2003-519901 gazette JP 2005-154895 A JP 2007-318177 A

  An object of the present invention is to provide a metal-coated polyimide resin substrate having high adhesion after aging for 150 ° C. and 168 hours without reducing the initial adhesion between the metal-coated polyimide resin film and the metal layer.

In view of the above problems, the present invention provides the following inventions.
1) After surface modification by a dry method on one or both sides of a polyimide resin film, a barrier layer is formed by a dry method, and then a seed layer is formed by a wet method or a dry method, and the surface layer is formed by a wet method. A time-of-flight secondary ion mass spectrometer (TOF) on a peeled surface of a metal-coated polyimide resin substrate on which a conductive film is formed and the metal-coated polyimide resin substrate is subjected to a 90 ° peel test on the conductive film layer side. -SIMS), the mixed layer thickness of the polyimide residue and the barrier metal layer residue by the depth direction analysis is 0.70 nm or less in terms of Si sputtering rate, and the peel strength retention after the aging test at 150 ° C for 168 hours ( A metal-coated polyimide resin substrate having a peel strength after aging for 150 ° C. for 168 hours / initial peel strength) of 50% or more.

The present invention provides the following invention.
2) The metal-coated polyimide resin substrate according to 1) above, wherein the seed layer and the conductive film are copper, and the barrier layer is nickel, chromium, or an alloy thereof.
3) The metal-coated polyimide resin substrate as described in 1) or 2) above, wherein surface modification of the polyimide resin film by a dry method is performed by plasma treatment.

  In the present invention, after surface modification by a dry method is performed on one or both sides of a polyimide resin film, a barrier layer is formed by a dry method, and then a seed layer is formed by a wet method or a dry method, and the surface layer is wet. This is a metal-coated polyimide resin substrate on which a conductive film is formed by the method. Especially, it has the excellent effect that the adhesion after aging can be enhanced without reducing the initial adhesion after lamination between the polyimide film and the metal layer. Have.

It is a figure which shows the result of having investigated the mixed layer thickness of a polyimide residue (CC) and a barrier metal (Ni) layer residue using the depth direction analysis of a time-of-flight type secondary ion mass spectrometer (TOF-SIMS). is there. It is a figure which shows the relationship with the peel strength retention (%) with respect to the thickness (Si conversion thickness nm) of a barrier metal and PI (polyimide) mixed layer.

In general, after surface modification by a wet method or a dry method on one or both sides of a polyimide resin film, a barrier layer is formed, a seed layer is formed on the barrier layer, and a constant thickness is formed on the seed layer. A metal-coated polyimide resin substrate is manufactured by forming a conductive film. In this invention, in order to form a barrier layer on a polyimide resin film, it can carry out by dry methods, such as sputtering, CVD, vapor deposition.
Non-adhesive flexible laminates (especially two-layer flexible laminates) that do not have an adhesive layer between the polyimide film and the metal layer produced in this way are circuits in the electronics industry as FCCL (Flexible Copper Clad Laminate). Although widely used as a substrate material, it is required to increase the adhesion between the metal layer and the polyimide film with the recent finer pitch of circuit wiring width.

As its evaluation method, it is generally performed to measure normal peel strength (initial peel strength) and heat-resistant peel strength (150 ° C, peel strength after 168 hours aging), which is an accelerated deterioration test.
As described above, since the peel strength after a long period of time has become particularly important as a requirement for high reliability, the peel strength retention rate (heat-resistant peel strength / normal peel strength) after an aging test at 150 ° C. and 168 hours is obtained. It is required to increase as much as possible.

  In order to increase the peel strength retention rate, it is known that the surface of the polyimide resin film is preferably subjected to a surface modification treatment by a wet method or a dry method, but this is due to any mechanism or phenomenon. Whether the peel strength increases is not fully understood, and there is a problem that it is difficult to maintain a certain reforming level to the extent that the reforming process itself is carried out by trial and error.

For this reason, the inventor of the present application investigated in detail the structure in the depth direction on the metal layer side peeling surface at 90 ° peel of the metal-coated polyimide resin substrate. As a result, it was found that there was a layer in which a barrier layer (nickel, chromium, or an alloy layer thereof) formed after the surface modification treatment and polyimide were mixed.
Although depending on the modification method of the polyimide resin, generally, if the modification process is excessive, the barrier layer metal is mixed into the polyimide modified layer, and there is a layer in which the barrier layer metal and the polyimide are mixed. Become thicker. Further, as the sputtering energy in the formation of the barrier layer increases, the barrier metal is more heavily implanted into the polyimide layer, and the layer in which the barrier layer metal and polyimide are mixed becomes thicker.
And it turned out that the peel strength fall after heat-resistant aging originates in the thickness of the mixed layer of the polyimide by the side of a metal layer and a barrier metal layer in an initial peel peeling surface. In other words, the thicker the mixed layer of polyimide and barrier layer metal, the more easily the copper having catalytic oxidation action diffuses into the polyimide layer through this mixed layer, so the deterioration of the molecular structure of the polyimide resin is promoted and the heat aging It has been found that the peel strength decreases.
Therefore, by adjusting the thickness of the polyimide and metal mixed layer on the metal layer side peeling surface in the initial peel, it is possible to maintain high peel strength after heat aging, and the initial metal layer side peeling surface. It was found that the peel strength after heat aging can be predicted from the thickness of the polyimide and metal mixed layer.

FIG. 1 shows a polyimide residue (C-C) and a barrier metal (Ni) layer using a depth direction analysis of a time-of-flight secondary ion mass spectrometer (TOF-SIMS) for the peel-off surface on the metal layer side. The outline when the mixed layer thickness of the residue is investigated is shown.
As shown in FIG. 1, the polyimide residue (C-C) has a peak at a sputtered Si equivalent depth of 2 nm, while the barrier metal (Ni) has a peak at a sputtered Si equivalent depth of 4.5 nm. . The middle is a mixed layer of polyimide and metal.
As is apparent from Examples and Comparative Examples described later, it has been found that the increase in the thickness of the mixed layer causes a decrease in the peel strength retention after heat aging.

  From the above, the inventors of the present invention have found that the mixed layer thickness of polyimide and barrier layer metal on the metal layer side peeled surface is 0.70 nm or less in terms of Si sputtering rate by TOF-SIMS depth direction analysis. It was found that the peel strength retention (heat-resistant peel strength / normal peel strength) after an aging test at 150 ° C. for 168 hours was increased. In this case, a peel strength retention of 50% or more can be achieved.

  Next, description will be made based on examples and comparative examples. In addition, a present Example is an example to the last, and is not restrict | limited only to this example. That is, other aspects or modifications included in the present invention are included.

Example 1
As a polyimide resin film, DuPont: Kapton 150EN was used. This polyimide resin film was subjected to plasma treatment, and a barrier layer made of a nickel chromium alloy was formed to a thickness of 25.0 nm by sputtering.
Next, a seed copper layer was formed by sputtering. Subsequently, an 8 μm copper conductor layer was formed by electroplating and the peel strength was measured. As a result, a sample having peel properties of a normal peel strength of 0.66 kN / m and a heat-resistant peel strength of 0.36 kN / m was obtained. .
For the metal-coated polyimide resin substrate formed in this way, the thickness of the mixed layer of the polyimide and the seed layer metal on the metal layer-side release surface in the normal peel is measured using a time-of-flight secondary ion mass spectrometer (TOF-SIMS). Measurements were made using depth direction analysis.
FIG. 2 is a diagram showing the relationship between the barrier metal and the peel strength retention rate (%) with respect to the thickness of the PI (polyimide) mixed layer (Si equivalent thickness nm). As shown in FIG. The thickness of the metal (Ni) and polyimide mixed layer was 0.53 nm in terms of Si, and the peel strength retention (heat-resistant peel strength / normal peel strength) at this time was a good result of 55%.
The results of the measurement are shown in Table 1.

(Example 2)
As a polyimide resin film, DuPont: Kapton 150EN was used. This polyimide resin film was subjected to plasma treatment, and a barrier layer made of a nickel chromium alloy was formed to a thickness of 25.0 nm by sputtering.
Next, a seed copper layer was formed by sputtering. Subsequently, an 8 μm copper conductor layer was formed by electroplating, and the peel strength was measured. As a result, a sample having peel properties with a normal peel strength of 0.80 kN / m and a heat-resistant peel strength of 0.48 kN / m was obtained.
For the metal-coated polyimide resin substrate formed in this way, the thickness of the mixed layer of the polyimide and the seed layer metal on the metal layer-side release surface in the normal peel is measured using a time-of-flight secondary ion mass spectrometer (TOF-SIMS). Measurements were made using depth direction analysis.
As a result, as shown in FIG. 2, the thickness of the barrier metal (Ni) and polyimide mixed layer is 0.41 nm in terms of Si, and the peel strength retention (heat-resistant peel strength / normal peel strength) at this time is 55%. And good results.
The results of the measurement are shown in Table 1.

(Comparative Example 1)
As a polyimide resin film, DuPont: Kapton 150EN was used. This polyimide resin film was subjected to plasma treatment, and a barrier layer made of a nickel chromium alloy was formed to a thickness of 25.0 nm by sputtering.
Next, a seed copper layer was formed by sputtering. Subsequently, an 8 μm copper conductor layer was formed by electroplating, and the peel strength was measured. As a result, a sample having peel properties with a normal peel strength of 0.79 kN / m and a heat-resistant peel strength of 0.38 kN / m was obtained.
For the metal-coated polyimide resin substrate formed in this way, the thickness of the mixed layer of the polyimide and the seed layer metal on the metal layer-side release surface in the normal peel is measured using a time-of-flight secondary ion mass spectrometer (TOF-SIMS). Measurements were made using depth direction analysis.
As a result, as shown in FIG. 2, the thickness of the barrier metal (Ni) and polyimide mixed layer is 0.77 nm in terms of Si, and the peel strength retention (heat-resistant peel strength / normal peel strength) at this time is 48%. It was bad.
The results of the measurement are shown in Table 1.

(Comparative Example 2)
As a polyimide resin film, DuPont: Kapton 150EN was used. This polyimide resin film was subjected to plasma treatment, and a barrier layer made of a nickel chromium alloy was formed to a thickness of 25.0 nm by sputtering.
Next, a seed copper layer was formed by sputtering. Subsequently, an 8 μm copper conductor layer was formed by electroplating, and the peel strength was measured. As a result, a sample having peel properties of a normal peel strength of 0.77 kN / m and a heat-resistant peel strength of 0.31 kN / m was obtained. .
For the metal-coated polyimide resin substrate formed in this way, the thickness of the mixed layer of the polyimide and the seed layer metal on the metal layer-side release surface in the normal peel is measured using a time-of-flight secondary ion mass spectrometer (TOF-SIMS). Measurements were made using depth direction analysis.
As a result, as shown in FIG. 2, the thickness of the barrier metal (Ni) and polyimide mixed layer is 0.97 nm in terms of Si, and the peel strength retention (heat-resistant peel strength / normal peel strength) at this time is 40%. It was bad.
The results of the measurement are shown in Table 1.

  From the above, as the mixed layer thickness of Ni and polyimide measured by TOF-SIMS increases, the peel strength retention rate (heat-resistant peel strength / normal peel strength) tends to decrease, and polyimide residue and barrier metal layer residue It was confirmed that the thickness of the mixed layer was 0.70 nm or less in terms of Si sputtering rate, and the peel strength retention rate was required to be 50% or more.

  In the present invention, after surface modification by a dry method is performed on one or both sides of a polyimide resin film, a barrier layer is formed by a dry method, and then a seed layer is formed by a wet method or a dry method, and the surface layer is wet. Time-of-flight secondary ion mass spectrometer on a peeled surface on the conductive coating layer side after a 90 ° peel test of the metal-coated polyimide resin substrate with a conductive coating formed by the method The mixed layer thickness of polyimide residue and barrier metal layer residue by depth direction analysis using (TOF-SIMS) is 0.70 nm or less in terms of Si sputtering rate, and the peel strength retention after aging test at 150 ° C. for 168 hours The metal-coated polyimide resin substrate is characterized in that the ratio (heat-resistant peel strength / normal peel strength) is 50% or more. Without lowering the initial adhesion after lamination between the polyimide film and the metal layer, the adhesion after aging is enhanced, and therefore it has an excellent effect in fine pattern formation, such as flexible printed circuit boards, TAB, COF, etc. It is useful as a non-adhesive flexible laminate material used as a component mounting material, particularly as a metal-coated polyimide resin substrate having excellent peel strength retention.

Claims (3)

  After surface modification by a dry method on one or both sides of a polyimide resin film, a barrier layer is formed by a dry method, and then a seed layer is formed by a wet method or a dry method, and the surface layer is conductive by a wet method. A metal-coated polyimide resin substrate on which a film is formed, and a time-of-flight secondary ion mass spectrometer (TOF-SIMS) is formed on a peeling surface on the conductive film layer side after the 90 ° peel test of the metal-coated polyimide resin substrate. ), The mixed layer thickness of the polyimide and the barrier layer metal is 0.70 nm or less in terms of Si sputtering rate, and the peel strength retention after the aging test at 150 ° C. and 168 hours (150 ° C. 168 hours after aging peel strength / initial peel strength) is 50% or more.   The metal-coated polyimide resin substrate according to claim 1, wherein the seed layer and the conductive film are copper, and the barrier layer is nickel, chromium, or an alloy thereof. The metal-coated polyimide resin substrate according to claim 1 or 2, wherein surface modification of the polyimide resin film by a dry method is performed by plasma treatment.

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